An investigation on the influence of solar cycle on mesospheric temperature

Mohanakumar, K.

doi:10.1016/0032-0633(85)90033-9

Cited by 32 publications

(17 citation statements)

References 23 publications

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“…We now compare our results in the lower mesosphere with those obtained in Heiss Island, published by Mohanakumar [1985]. In winter they find large amplitudes between solar maximum and solar minimum in the order of 30 K at 65 km which is much larger than what we observe, regardless of the definition of the QBO phase transition and/or the averaging period.…”

Section: The Correlation Coefficients Between Daily Averaged Temperatmentioning

confidence: 83%

Thermal structure of the mesopause region at polar latitudes

Lübken¹,

Zahn²

1991

J. Geophys. Res.

205

117

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We present the results of temperature soundings performed on almost 180 days since 1980 in the 50to 120-km altitude range at Andenes, Norway (69øN latitude). Most of the temperature profiles were obtained by ground-based lidar; the others were derived from in situ density measurements. We present (1) monthly mean temperatures for 9 months of the year, including the mesopause temperature and altitude, and examine (2) seasonal effects, (3) interannual variability, (4) systematic differences to CIRA 1986, and (5) longer-term effects related to the solar activity cycle. The main results are as follows: the mesopause is high (98 km) and warm (192 K) in a long period from October to March and low (88 km) and cold (129 K) in June and July. The transition between these two states in August is much faster than commonly anticipated. An intercomparison of our monthly mean temperature profiles with CIRA 1986 shows significant deviations. Above 80 km we find positive correlations between temperature and solar activity with regression coefficients in the order of 0.15 K/SFU. 1.altitudes below 75-80 km and therefore do not cover the mesopause region. During the last 10 years we have obtained at 69øN latitude (Andenes, Norway) temperature profiles on approximately 180 days in this part of the atmosphere. Our measurements cover the altitude range from 50 to 120 km, though with different statistics. The purpose of this paper is to summarize (1) the results of our measurements and to examine (2) seasonal effects, (3) interannual variability, (4) systematic differences to existing reference atmospheres, and (5) longer-term effects related to solar cycle. MEASUREMENT TECHNIQUESTemperature profiles were measured directly by a sodium lidar and were deduced from density measurements performed by passive falling spheres, ionization gauges, and mass spectrometers. Details of the instruments and of the data reduction are presented elsewhere (see below). Here we will only summarize the most important characteristics of the experiments.The sodium lidar allows to measure temperature profiles in the altitude region 80 to 110 km from the measurement of the 20,841 20,842 LOBKEN AND VON ZAHN: THERMAL STRUCTURE OF THE POLAR MESOPAUSE REGION Doppler broadening of the laser-excited sodium D 2 resonance line of free sodium atoms. For integration periods of 10 min the altitude resolution is 1 km between 80 and 100 km and 2 km above. To acquire temperature data, the instrument needs clear sky and darkness. With this technique, winter conditions were investigated by Neuber et al. [1988] and late summer conditions by Kurzawa and yon . Here we employ recent theoretical results of yon der Gathen [1991] to correct in retrospect some of our measured temperatures for small, higher order effects caused by the finite natural linewidth of the Na hyperfine structure absorption lines and Na saturation effects. The total corrections are small (typically -4 K) and depend on instrumental and atmospheric parameters, such as the laser beam divergence, the energy of t...

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Section: The Correlation Coefficients Between Daily Averaged Temperatmentioning

confidence: 83%

Thermal structure of the mesopause region at polar latitudes

Lübken¹,

Zahn²

1991

J. Geophys. Res.

205

117

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“…The Solar Mesosphere Explorer (SME) data show a −1.0 K/yr cooling at 76 km over the equator [ Clancy and Rush , 1989] during 1982–1986, which was also attributed to the declining phase of the solar cycle. Rocket observations from 1975–1980 have suggested 20 K increases for mesospheric temperatures in the 65‐ to 70‐km altitude region, which was correlated with the solar minimum to solar maximum cycle over the same period [ Mohanakumar , 1985; Groves , 1986]. Chanin et al [1987], using lidar data, observed the temperature decrease of comparable magnitude at the same altitude for the solar maximum to solar minimum (1981–1986) period.…”

Section: Resultsmentioning

confidence: 99%

Further evidence of a two‐level mesopause and its variations from UARS high‐resolution Doppler imager temperature data

Thulasiraman

Nee

2002

J.‐Geophys.‐Res.

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[1] The temperature data from the High Resolution Doppler Imager on board the Upper Atmospheric Research Satellite are used to study mesospheric dynamics. Data spread over 7 years (1992)(1993)(1994)(1995)(1996)(1997)(1998) in the height region of 75-105 km are analyzed to study the seasonal and long-term changes in the mesopause height and temperatures. During December solstice (1992), the mesopause is at the high level of 100 km in the Northern Hemisphere with a temperature of 190 K, and around 40°S, the mesopause changes to a low level of 88 km with a cool temperature (150 K) of 40 K less than the high-level mesopause. In June solstice (1993), the mirror image of this pattern is observed. This kind of two-level mesopause structure is consistently seen during all solstices at the same height and the transition occurring at the same latitudes. The high-level mesopause with temperatures of 180-190 K and the low-level mesopause with temperatures of 140-150 K are observed. The two-level mesopause is not observed in equinoxes, and a single-level mesopause is seen around 100-km altitude in both hemispheres. The annually averaged temperature data show 5 K warming of high-level mesopause during 1992 and 1993, which may be due to Pinatubo volcanic aerosols. This warming is comparable but less than the 9 K warming at 100-km height observed by She et al.[1998] at 41°N. The time series analysis of temperature at 99 km shows a decrease of 1.2 ± 0.15 K/yr over the equatorial region during 1992-1998. The lowest mesopause temperatures at northern high latitudes are observed between May and August, which is consistent with the period of polar mesosphere summer echo observed by using VHF radar at these latitudes.

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“…At mid and high latitude, the signal was more difficult to extract from the large atmospheric variability. On the 11-year timescale, various atmospheric responses were obtained, varying from slightly positive to negative (Mohanakumar, 1985;Kokin et al, 1990;Hauchecorne et al, 1991), leading to inconclusive results. Chanin et al (1989) combined different data sets, showing a negative response that has vertical features of alternating sign.…”

Section: Introductionmentioning

confidence: 92%